add grid system and style examples.jsx

app/components/Main.jsx

@@ -18,11 +18,14 @@ var Main = (props) => {
   return (
     <div>
       <Nav/>
-      <h2>Main Component</h2>
-      {props.children}
+      <div className="row">
+        <div className="columns medium-6 large-4 small-centered">
+          {props.children}
+        </div>
+      </div>
     </div>
 
   );
-};
+}
 
 module.exports = Main;